The present invention generally relates to the manufacture of semiconductor devices and in particular, to a method for forming localized halo implant regions.
The usefulness of halo implant regions to reduce undesirable short channel effects such as punch-through leakage in CMOS FET semiconductor devices is well known. Conventional methods for forming such halo implant regions, however, are also known to generate undesirable sheet resistance characteristics resulting in increased threshold voltages and resistances at the source and drain contact points, that increasingly worsen as device feature sizes shrink. Another common drawback of such conventionally formed halo implant regions is increased junction capacitance. Since many halo-implanted ions are located near the junction of the heavily doped source/drain and substrate, the junction capacitance value becomes significantly increased. Since this tends to reduce circuit speed, it is a major factor in limiting the amount of the halo implant dose.
Accordingly, it is an object of the present invention to provide a method for forming a localized halo implant region that provides generally improved sheet resistance and junction capacitance characteristics.
Another object is to provide a method for forming a localized halo implant region that is cost effective to manufacture.
These and additional objects are accomplished by the various aspects of the present invention, wherein briefly stated, one aspect is a method for forming a localized halo implant region, comprising: tilt-angle implanting at least one dosage of ions toward a gap created by removal of a disposable spacer between a gate electrode and an elevated source/drain structure on a substrate so as to form a localized halo implant region in the substrate.
In another aspect, a method for forming a localized halo implant region, comprising: implanting a first dosage of ions of a first type toward a surface of a substrate having a gate electrode formed thereon, so as to form a lightly doped region adjacent to the gate electrode; forming a disposable spacer on a sidewall of the gate electrode; forming an elevated source/drain structure adjacent to the disposable spacer; implanting a second dosage of ions of the first type toward the surface of the substrate so as to form a heavily doped region adjacent to the disposable spacer; removing the disposable spacer; and tilt-angle implanting at least one dosage of ions of a second type toward a gap created by the disposable spacer having been removed, so as to form a localized halo implant region in the substrate.
Additional objects, features and advantages of the various aspects of the present invention will become apparent from the following description of its preferred embodiment, which description should be taken in conjunction with the accompanying drawings.